A decolorable material is known whose colors are erased when heated up to a predetermined color erasing temperature. A sheet on which an image is formed by the decolorable material may be reused since the colors of the image are be erased when a color erasing apparatus heats the sheet up to the predetermined color erasing temperature.
However, in the above-described related art, the colors of the image may be only entirely erased, and it is not possible to partially erase the colors of the image. Accordingly, there is a need to develop a color erasing technology which may be used in various applications